A variable resistor assembly is often used with a fuel level sensor to detect a change in fuel level in a fuel tank of an automobile. A typical variable resistor assembly includes a resistor that is variable so that its resistance value may be changed by mechanical movement of a wiper, which is attached to a float responsive to changes in fuel level in the fuel tank. The typical variable resistor assembly may include the wiper, a resistor card including a ceramic substrate, two separate terminals on the substrate, and two separate and respective arcuate resistive areas on the substrate that are electrically connected with the terminals. The arcuate resistive areas may be segmented into a plurality of conductive contact segments. The wiper bridges the resistive areas to complete the variable resistor, is pivotably mounted in relation to the resistor card, and has one or more contactors adapted for contacting the arcuate resistive areas as the wiper sweeps thereacross.
A typical fuel level sensor includes a float linked to the wiper of the variable resistor assembly by an actuator arm to vary the resistance value of the resistor in accordance with the position of the float. As the level of fuel within a fuel tank changes, the float member and actuator arm move and thereby cause the wiper to slide over the arcuate resistive areas to change an effective length of the variable resistor between the terminals and thereby vary the effective resistance of the variable resistor. In accordance with the change in resistance, the output voltage of the resistor card changes and, thus, effects a change—such as from “Full” toward “Empty”—in a remote fuel level indicator.
In use, existing fuel level sensors may have drawbacks. For example existing fuel level sensors can perform erratically when a wiper contactor falls in between, and momentarily out of contact with, adjacent conductive contact segments of the resistive area. In other words, a portion of the variable resistor is momentarily opened or interrupted, thereby causing voltage spikes to be output from the fuel level sensor to a liquid level indicator. Another problem involves “catching” of wiper contactor comers on angled conductive contact segments of an arcuate resistive area. When a wiper sweeps across the resistive area, the sharp corners of the contactors can “catch” on the angled conductive contact segments, thereby causing noisy operation of the variable resistor.